I've been searching everywhere in the unova region and can't find a dusk stone. I really want my lampent to evolve :( and what do I do with a thunderstone? I know there aren't any pokemon that evolve with it in black

Duskclouds is where you can find stones. Also you can get a dusk stone on route ten from a guy on the bridge you will have to go through the area of double grass. And thunderstones can be used to evolve the evolution of tynamo(forgot middle evolution's name) to get it to its final form.

Actually, there is a Pokemon that can evolve with the Thunderstone in White and Black and it's name is Elektrik, which will evolve into Elecktross and you can get a Duskstone in Black at Black City in the store in the middle of the city but you have to buy it. (Hope This Helps!). :)